| Obrien, James | Firefighter Paramedic 112 Hour (On Or After 1-1-2016) | Fire | 949-644-3355 | |
| O'Campo, Kevin | Public Works Inspector I | Public Works | 949-718-3410 | |
| O'Campo, Kevin | Utilities Crew Chief | Utilities | 949-718-3410 | |
| Ochoa Cruz, Iliana | Contractor | Public Works | | |
| Ochoatenorio, Heriberto | Contractor | Public Works | | |
| Oconnor, Pamela | Library Clerk I | Library - City | 949-717-3851 | |
| Odom, Denise | Recreation Leader, Senior | Recreation & Senior Services | | |
| O'Keefe, David | Lifeguard II | Fire | | |
| Olazo, Blanca | Senior Services Shuttle Driver | Recreation & Senior Services | 949-644-3244 | |
| O'Leary, Ryan | Firefighter Paramedic 112 Hour (Before 1-1-2016) | Fire | 949-644-3104 | |
| Olivieri, Luca | Intern | Community Development | 949-644-3215 | |
| Olsen, Kaden | Lifeguard I | Fire | | |
| Ordaz, Jocelyn | Recreation Leader, Senior | Recreation & Senior Services | | |
| Ordiano, Omar | Recreation Supervisor | Recreation & Senior Services | 949-718-1993 | |
| Ordonez, Alfredo | Contractor | Public Works | | |
| O'Rourke, Brian | Assistant Chief, Lifeguard Operations | Fire | 949-644-3045 | |
| Orozco, Oscar | Planner, Associate | Community Development | 949-644-3219 | |
| Ortez, Francisco | Utilities Specialist | Utilities | 949-718-3461 | |
| Ortiz, Ryan | Lifeguard I | Fire | | |
| Osadche, Zachary | Harbor Services Worker | Harbor Department | | |
